In the aging process, various signs appear on the skin resulting from a modification of skin structure and of cutaneous function. The main clinical signs of aging are, among others, the appearance of fine wrinkles and deep wrinkles. These signs of aging increase with age. A disorganization of skin “texture” is more particularly observed, meaning that micro-contours are less regular and show an anisotropic character.
It is known to treat these signs of aging using cosmetic or dermatological compositions containing actives adapted to fight against such signs of aging, such as α-hydroxy-acids, β-hydroxy-acids and retinoids. Such actives act on wrinkles primarily by eliminating dead skin cells and accelerating the cell renewal process.
However, the visible effect of such compositions is generally observed after some application time, ranging from a few days to several weeks.
Several compositions have been suggested which have a tensing effect, making it possible to obtain an immediate skin smoothing.
Such compositions generally contain as a tensing agent substances from natural origin, such as plant, egg, milk or animal derivatives. For instance, the International Application WO-98/29091 discloses the use, as a tensing agent, of a polymeric system having particular physico-chemical properties and comprising at least one polymer from natural origin, such as a soya protein extract or chitin or keratin derivatives. Moreover, the International Application WO 96/19180 discloses toning compositions comprising a film-forming agent containing at least one plant polysaccharide and hydrolyzed casein as tensing actives. However, the use of substances from natural origin is limited by hazards associated with bovine spongiform encephalopathy. Moreover, not only are tensing effects not always reproducible, but the tensing effect obtained from such substances is not very significant from a qualitative standpoint, and from a quantitative standpoint, the effect shows a low remanence.
Other prior art compositions having a tensing effect use synthetic polymers. PCT Application WO-98/29022 discloses a composition having a tensing effect and comprising an aqueous dispersion of a polymeric system containing at least one polymer from plastic origin selected from the group comprising several types of polyurethanes, polyureas, acrylic polymers or copolymers, sulfonated isophthalic acid polymers and the mixtures thereof. The cosmetic feel of such compositions is, however, not satisfactory.
Additionally, European Patent Application EP-1038519-A1 discloses the use as a tensing agent in and/or for the manufacture of an anti-wrinkle composition, of at least one grafted silicone polymer comprising one polysiloxane portion and one portion consisting of a non silicone organic chain, one of the two portions constituting the main chain and the other one being grafted on said main chain. However, such silicone polymers do not exhibit satisfactory anti-wrinkle effects when they are formulated in an emulsion.
The use of mineral fillers and more particularly of silica in cosmetic compositions is known. For instance, silica is a widely used material in the cosmetic industry. It confers softness and a matte aspect to the formulations. It is also used in association with titanium dioxide or zinc oxide for forming complex particles with sun filter effects. For such applications, silica is very often in pulverulent form and a wide range of particle sizes is available from 1 μm to 100 μm. However it is far less usual, and even exceptional, to use colloid particles.
European Patent Application EP-1 008 334-A2 discloses the use and preparation, at an acidic pH, of mixed silicates, as tensing agents, for tensing and smoothing the skin, in order to immediately attenuate the skin wrinkles and/or fine wrinkles, the mixed silicates being in the form of particles having an average size ranging from 15 to 1000 nm resulting in colloid solutions. However, nothing is mentioned regarding fillers other than mixed silicates. Moreover, the tensing effect and the smoothing power are attributed to the chemical nature of the mixed silicates and not to the particle size.
Accordingly, there remains a need for compounds offering an immediate tensing effect, which are satisfactory and durable, which do not pose any risk for the consumer and are able to be formulated in compositions comprising fatty phases. The present invention precisely aims at meeting such a need.